Add missing @Override annotations

This commit also adds MissingOverrideCheck module to Checkstyle configuration.

samples/xml/contacts/src/main/java/sample/contact/Contact.java

@@ -84,6 +84,7 @@ public class Contact implements Serializable {
 		this.name = name;
 	}
 
+	@Override
 	public String toString() {
 		StringBuilder sb = new StringBuilder();
 		sb.append(super.toString() + ": ");

samples/xml/dms/src/main/java/sample/dms/Directory.java

@@ -31,6 +31,7 @@ public class Directory extends AbstractElement {
 		super(name, parent);
 	}
 
+	@Override
 	public String toString() {
 		return "Directory[fullName='" + getFullName() + "'; name='" + getName()
 				+ "'; id='" + getId() + "'; parent='" + getParent() + "']";

samples/xml/dms/src/main/java/sample/dms/File.java

@@ -39,6 +39,7 @@ public class File extends AbstractElement {
 		this.content = content;
 	}
 
+	@Override
 	public String toString() {
 		return "File[fullName='" + getFullName() + "'; name='" + getName() + "'; id='"
 				+ getId() + "'; content=" + getContent() + "'; parent='" + getParent()

samples/xml/jaas/src/main/java/samples/jaas/UsernameEqualsPasswordLoginModule.java

@@ -44,14 +44,17 @@ public class UsernameEqualsPasswordLoginModule implements LoginModule {
 	// ~ Methods
 	// ========================================================================================================
 
+	@Override
 	public boolean abort() throws LoginException {
 		return true;
 	}
 
+	@Override
 	public boolean commit() throws LoginException {
 		return true;
 	}
 
+	@Override
 	public void initialize(Subject subject, CallbackHandler callbackHandler,
 			Map<String, ?> sharedState, Map<String, ?> options) {
 		this.subject = subject;
@@ -70,6 +73,7 @@ public class UsernameEqualsPasswordLoginModule implements LoginModule {
 		}
 	}
 
+	@Override
 	public boolean login() throws LoginException {
 		if (username == null || !username.equals(password)) {
 			throw new LoginException("username is not equal to password");
@@ -82,6 +86,7 @@ public class UsernameEqualsPasswordLoginModule implements LoginModule {
 		return true;
 	}
 
+	@Override
 	public boolean logout() throws LoginException {
 		return true;
 	}
@@ -93,10 +98,12 @@ public class UsernameEqualsPasswordLoginModule implements LoginModule {
 			this.username = username;
 		}
 
+		@Override
 		public String getName() {
 			return username;
 		}
 
+		@Override
 		public String toString() {
 			return "Principal [name=" + getName() + "]";
 		}

samples/xml/tutorial/src/main/java/bigbank/Account.java

@@ -65,6 +65,7 @@ public class Account {
 		this.overdraft = overdraft;
 	}
 
+	@Override
 	public String toString() {
 		return "Account[id=" + id + ",balance=" + balance + ",holder=" + holder
 				+ ", overdraft=" + overdraft + "]";